1. Field of the Invention
The present invention pertains to patient interface devices structured to deliver a flow of breathing gas to a patient, and, in particular, to patient interface devices employing a headgear component having a modular back strap to improve performance.
2. Description of the Related Art
There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e., without intubating the patient or surgically inserting a tracheal tube into the patient's esophagus. For example, it is known to ventilate a patient using a technique known as non-invasive ventilation. It is also known to deliver positive airway pressure (PAP) therapy to treat certain medical disorders, the most notable of which is OSA. Known PAP therapies include continuous positive airway pressure (CPAP), wherein a constant positive pressure is provided to the airway of the patient in order to splint open the patient's airway, and variable airway pressure, wherein the pressure provided to the airway of the patient is varied with the patient's respiratory cycle. Such therapies are typically provided to the patient at night while the patient is sleeping.
Non-invasive ventilation and pressure support therapies as just described involve the placement of a patient interface device including a mask component having a soft, flexible sealing cushion on the face of the patient. The mask component may be, without limitation, a nasal mask that covers the patient's nose, a nasal/oral mask that covers the patient's nose and mouth, a nasal cushion that rests beneath the patient's nose (such as a “pillows” style nasal cushion having nasal prongs that are received within the patient's nares or a “cradle” style nasal cushion that rests beneath and covers the patient's nares), or a full face mask that covers the patient's face. Such patient interface devices may also employ other patient contacting components, such as forehead supports, cheek pads and chin pads. The patient interface device is connected to a gas delivery tube or conduit and interfaces the ventilator or pressure support device with the airway of the patient, so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient.
It is known to maintain such devices on the face of a wearer by a headgear having one or more straps adapted to fit over/around the patient's head. One popular patient interface device 2 is shown in FIGS. 1 and 2. As seen in FIGS. 1 and 2, patient interface device 2 includes a nasal mask 4 for providing a seal and delivering a breathing gas to the patient's airway, and a headgear apparatus 6 for securing patient interface device 2 to the patient's head. Headgear apparatus 6 includes a first strap 8 that extends from nasal mask 4 at the patient's nose to the crown of the patient's head and a second strap 10 which attaches to first strap 8 above the ear and wraps around the back of the patient's head/neck.
Patient interface devices like patient interface device 2 are extremely appealing to patients due to their minimal size and straps. Because of this, patients will very often initially choose a device of this type, but will experience problems with second strap 10 riding up on the back of the head while they are asleep. Such riding often results in patient interface device 2, and in particular nasal mask 4, becoming dislodged from the face as shown in FIG. 2. In many cases, the patient will then request a new patient interface device with a different headgear configuration. This costs the supplier a new patient interface device and requires someone, such as a respiratory therapist, to take time to fit the patient with a completely different device.
In addition, the forces applied to nasal mask 4 by this type of headgear apparatus may be less than optimal because nasal cushions such as nasal cushion 4 typically work better when the forces applied to the nose bridge and upper lip can be adjusted independently to achieve proper cushion orientation with respect to the face. Having another strap for the mask 4 is adventitious not only for the initial adjustment, but it also aids in helping stabilize the mask while the patient is sleeping. Without the addition of a stabilization strap the mask could become dislodged during sleep thus causing interruptions to therapy delivery.